Height adjustable spinal prostheses

ABSTRACT

Dimensionally adjustable spinal prostheses are adjustable in an axial or superior to inferior dimension such that spinal prostheses may assume variations in height. The height adjustable spinal prostheses are characterized by first and second portions that are configured for adjustable coupling with one another. Spatial adjustment between the first and second portions is provided by an adjustment assembly. The adjustment mechanism preferably, but not necessarily, provides infinite adjustment over a minimum prosthesis height to a maximum prosthesis height. In one form, first and second ends of the height adjustable spinal prostheses are configured to receive an endplate. The endplates aid in attachment and/or anchoring of the spinal prosthesis within the spine. The endplates may be fashioned in various configurations such as circular or anatomical. In one form, the adjustment assembly utilizes rotational motion for varying the axial position of one prosthetic portion relative to the other prosthetic portion. Rotational movement of an adjustment mechanism of the adjustment assembly is translated into axial movement of one prosthetic portion relative to the other prosthetic portion. In another form, the adjustment mechanism is a screw and gearing assembly. In yet another form, the adjustment mechanism is a rack and pinion assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 12/079,670, filed Mar. 29, 2008, entitled “Height AdjustableSpinal Prostheses,” which claims the benefit of and/or priority to U.S.Provisional Patent Application Ser. No. 60/920,699 filed Mar. 29, 2007,entitled “Height Adjustable Spinal Prosthesis,” both of which areincorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to relates to spinal prostheses and, moreparticularly, to dimensionally adjustable spinal prostheses.

Background Information

Vertebrae and/or discs of a human spine can sometimes be damaged due todisease or injury, may be malformed through a congenital defect or cansimply deteriorate due to age. In other cases, vertebrae and/or discsmay become fractured, compressed or otherwise damaged. In these andother situations the vertebrae and/or discs can cause an undesiredand/or abnormal curvature of the spine with respect to lordosis orkyphosis.

Because of this, orthopedic surgery may be utilized to replace one ormore vertebrae or discs with a spinal prosthesis or one or morevertebrae may be repaired via kyphoplasty or vertebroplasty. In the caseof disc replacement, the spinal prosthesis may be used between adjacentvertebrae in order to provide proper spacing of the vertebrae. A spinalprosthesis may also be used to promote fusion between adjacentvertebrae. When so utilized, bone or bone fusion material is oftenplaced about or in the spinal prosthesis in order to promote growth ofbone between the adjacent vertebrae.

One type of spinal prosthesis may also be used in place of a vertebra ora vertebra and adjacent disc. The vertebra and disc are removed. Thistype of spinal prosthesis is then placed between remaining adjacentvertebrae as the middle vertebra has been removed. When this is thecase, the adjacent discs may also be removed.

When such spinal prostheses are used, it is desirable for them to engageas much surface of the vertebral bone as possible in order to providesupport to the bone and to thereby reduce the likelihood of subsidenceof the device into the bone resulting from contact pressure of theprosthesis against vertebral bone surfaces. Subsidence can occur sincepart of the vertebral bone is somewhat spongy in nature, especially nearthe centers of the adjacent vertebrae.

Because anatomical relationships for each patient are different, it isdesirable to have a spinal prosthesis that may be varied in variousdimensions. One such aspect is the height or axial (superior/inferior)length of the spinal prosthesis. As such, it is desirable to provide aspinal prosthesis that is dimensionally adjustable in height.Accordingly, there presently exists a need for height adjustable spinalprostheses.

SUMMARY OF THE INVENTION

The present invention provides height adjustable spinal prostheses. Theheight adjustable spinal prostheses may be used as vertebral prostheses,vertebral body replacement (VBR) prostheses, and/or spinal distractionprosthesis as appropriate. Other uses are contemplated.

The spinal prostheses are adjustable in an axial or superior to inferiordimension (height) such that spinal prostheses may assume variations inheight. Such height variation may be accomplished in situ.

The present height adjustable spinal prostheses are characterized byfirst and second prosthetic portions that are configured in adjustablecoupling with one another to effect height variation. Either prostheticportion may be adjusted relative to the other prosthetic portion or bothmay be adjusted. Spatial adjustment between the prosthetic portions isprovided by an adjustment assembly.

In one form, the prosthetic portions are adjustably coupled for axialdisplacement relative to one another or of one relative to the other inorder to effect overall prosthesis height variation. The adjustmentmechanism preferably, but not necessarily, provides infinite adjustmentover a minimum prosthesis height to a maximum prosthesis height.

In one form, first and second ends of the height adjustable spinalprostheses are configured to receive an endplate. The endplates aid inattachment and/or anchoring of the spinal prosthesis within the spine.The endplates may be fashioned in various configurations such ascircular or anatomical.

In one form, the adjustment assembly utilizes rotational motion forvarying the axial position of one prosthetic portion relative to theother prosthetic portion. Rotational movement of an adjustment mechanismof the adjustment assembly is translated into axial movement of oneprosthetic portion relative to the other prosthetic portion.

In one form, the adjustment mechanism is a screw and gearing assembly.In another form, the adjustment mechanism is a rack and pinion assembly.

The present modular height adjustable spinal prostheses may be implantedanteriorly, transversly and/or posteriorlaterally.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features, advantages and objects of thisinvention, and the manner of attaining them, will become apparent andthe invention itself will be better understood by reference to thefollowing description of embodiments of the invention taken inconjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view of an exemplary embodiment of a heightadjustable spinal prosthesis fashioned in accordance with the presentprinciples;

FIG. 2 is a perspective view of a lower portion of the height adjustablespinal prosthesis of FIG. 1;

FIG. 3 is a perspective view of an upper portion of the heightadjustable spinal prosthesis of FIG. 1;

FIG. 4 is a front view of a height adjustment portion of the heightadjustable spinal prosthesis of FIG. 1;

FIG. 5 is a first side view of the height adjustable spinal prosthesisof FIG. 1;

FIG. 6 is a sectional view of the height adjustable spinal prosthesis ofFIG. 5 taken along line 6-6 thereof;

FIG. 7 is a second side view of the height adjustable spinal prosthesisof FIG. 1;

FIG. 8 is a sectional view of the height adjustable spinal prosthesis ofFIG. 7 taken along line 8-8 thereof;

FIG. 9 is a third side view of the height adjustable spinal prosthesisof FIG. 1;

FIG. 10 is a perspective view of the height adjustable spinal prosthesisof FIG. 1 with endplates thereon;

FIG. 11 is an embodiment of an exemplary circular endplate for theheight adjustable spinal prosthesis of FIG. 1;

FIG. 12 is an embodiment of an exemplary anatomical endplate for theheight adjustable spinal prosthesis of FIG. 1;

FIG. 13 is an enlarged portion of an area of the anatomical endplate ofFIG. 12 labeled FIG. 13 in FIG. 12;

FIG. 14 is a side view of an endplate for the height adjustable spinalprosthesis of FIG. 1 particularly showing its slope or angle between anend of the endplate and a front of the endplate, the endplaterepresentative of all endplates for the height adjustable spinalprosthesis of FIG. 1;

FIG. 15 is a side sectional view of an exemplary embodiment of a rackand pinion type height adjustable spinal prosthesis fashioned inaccordance with the present principles;

FIG. 16 is a side sectional view of another exemplary embodiment of arack and pinion type height adjustable spinal prosthesis fashioned inaccordance with the present principles;

FIG. 17 is a side sectional view of another exemplary embodiment of arack and pinion type height adjustable spinal prosthesis fashioned inaccordance with the present principles; and

FIG. 18 is a perspective view of an exemplary embodiment of anotherheight adjustable spinal prosthesis fashioned in accordance with thepresent principles.

Like reference numerals indicate the same or similar parts throughoutthe several figures.

A detailed description of the features, functions and/or configurationof the components depicted in the various figures will now be presented.It should be appreciated however that not all of the features of thecomponents of the figures are necessarily described. Some of these nondiscussed features as well as discussed features are inherent from thefigures. Other non discussed features may be inherent in componentgeometry and/or configuration.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Referring to the figures and in particular FIGS. 1-9, there is depictedan exemplary embodiment of a height adjustable, adjustable height and/ordynamic spinal prosthesis or implant, generally designated 10, fashionedin accordance with the present principles. Height is axial orsuperior/inferior dimension of the prostheses when implanted in thespine. The height adjustable spinal prosthesis 10 is characterized bycomponents fabricated from a bio-compatible material such as stainlesssteel, titanium, a titanium alloy, composite, polymer or any combinationthereof. It should be appreciated that the height adjustable spinalprosthesis 10 is for use as a vertebral prosthesis, a vertebral bodyreplacement (VBR), a spinal distraction device and/or a fusion device asappropriate. It should be further appreciated that the height adjustablespinal prosthesis 10 may be fabricated in various sizes as appropriateto accommodate different anatomy sizes.

The height adjustable spinal prosthesis 10 is characterized by a loweror arbitrarily first prosthetic portion or assembly 12 (hereinafter andcollectively, lower portion 12), an upper or arbitrarily second portionor assembly 14 (hereinafter and collectively, upper portion 14) and anadjustment portion or assembly 16. In accordance with the principles ofthe present invention, one prosthetic portion is movable relative to theother prosthetic portion and particularly, but not necessarily, areaxially movable relative to one another. In the present embodiment, theupper portion 14 is axially movable relative to the lower portion 12through rotation of the height adjustment assembly 16 thereby providingadjustment in height of the spinal prosthesis 10. Particularly, theupper portion 14 is axially movable, displaceable or translatablerelative to the lower portion 12 through rotation of the heightadjustment assembly 16 such that the overall height of the spinalprosthesis 10 is adjustable from a minimum prosthesis height to amaximum prosthesis height depending on dimensions of the components. Theterms upper and lower are in relation to the preferred, but notnecessary, implantation orientation of the prostheses as implanted intothe spine, the head or the person being upper and the feet being thelower.

FIG. 2 depicts the lower portion 12 of the spinal prosthesis 10 ofFIG. 1. The lower portion 12 is defined by a polygonal body 22 having anopen top or upper end and a closed bottom or lower end enclosing anddefining an interior space or chamber 34 that opens into a threadedcentral shaft 41 of the body 22 (see e.g. FIGS. 6 and 8). Various sidesof the body 22 have an elongated opening 23. The elongated opening 23provides access to the interior 34 of the body 22. If desired, bonegrowth material may be received into the interior 34 via one or more ofthe openings 23 after assembly. The body 22 has first and second axialguides 66 and 67 in the walls of the body and opposite one another. Eachguide 66, 67 comprises an axial formation that defines an inner axialchannel. Each axial channel corresponds to and receives an axialprojection 64 and 69 of the upper portion 14. These features create anddefine an anti-rotation structure for the spinal prosthesis andparticularly the upper portion relative to the lower portion. The upperportion 14 is restrained from rotation relative to the lower portion 12so that rotational motion from the adjustment portion 16 is translatedinto axial or up/down movement of the upper portion 14 relative to thelower portion 12. Particularly, when the screw shaft 26 of theadjustment portion 16 rotates in the threaded bore 57 of the upperportion 14 (see, e.g., FIGS. 6 and 8), the rotational motion istranslated into axial or up/down motion of the upper portion 16 relativeto the lower portion 12.

The body 22 also includes a bore 60 on one side thereof and a port 62situated in the side thereof and axially below the bore 60. An input orbevel assembly 49 utilizes the bore 60 (see, e.g. FIG. 8). The inputbevel assembly 49 includes a polylobular or configured input socket 56(see, e.g., FIG. 9) by which the adjustment assembly 16 is actuated. Apolylobular or configured driving tool is utilized to rotate the inputbevel assembly 49. Rotation of the input bevel assembly 49 rotates theadjustment portion 16 to raise and lower the height of the spinalprosthesis 10. The port 62 is preferably threaded and thus adapted toreceive a threaded set pin or key 63 (see, e.g., FIG. 8). The threadedset pin 63 is utilized to prevent rotation of the input bevel gear 50 ofthe input bevel assembly 49 by extending into the teeth 52 of the inputbevel gear 50 when threaded into the port 62. The threaded set pin 63includes a hex or configured input socket 65 (see, e.g., FIG. 9) thatreceives a hex or configured driving tool to set the set pin 63 asappropriate.

The lower end of the body 22 further includes a hub 54 having an axialbore 55 therethrough (see, e.g. FIGS. 6 and 8) that extends from thelower end. A collar 48 partially surrounds or extends about the hub 54.The collar 48 controls angular freedom of end plates (see, e.g. FIGS.11-14) of and/or for the spinal prosthesis 10. A bore 68 is defined inthe body 22 that is configured to project into the interior 34 forcooperation with the slot 70.

FIG. 3 depicts the upper portion 14 of the spinal prosthesis 10 ofFIG. 1. The upper portion 12 is disposed in the interior 34 and isconfigured to axially move within the interior 34 in order to adjust theoverall height of the spinal prosthesis 10. The upper portion 14 isdefined by a generally polygonal body 20 having a hub 42 having an axialbore 46 therethrough (see, e.g. FIG. 8) that extends from the upper endthereof. A collar 43 partially surrounds or extends about the hub 42.The collar 43 controls angular freedom of end plates (see, e.g. FIGS.11-14) of and/or for the spinal prosthesis 10. Various sides of the body20 have ovoid openings 37, 39 and 41. If desired, bone growth materialmay be received into one or more of the openings 37, 39 and 41. The body20 has first and second axial guides 64 and 69 in the opposite walls ofthe body 20. The axial guides 64, 69 correspond with guides 66 and 67 ofthe lower portion 12 and co-act as described above. The body 20 also hasa cutout area that defines a projection 40, an undersurface or ledge 47of the projection 40 and a flat 38. As best seen in FIG. 8, the cutoutarea The projection 40 and flat 38 are sized such that when the upperportion 12 is at its lowest axial position and intermediate positionswithin the cavity 34 of the lower portion 14, the upper portion 12 willnot interfere with the bevel assembly 49 of the lower portion 14 (see,e.g. FIG. 8).

Referring particularly to FIG. 4, the height adjustment portion 16 ischaracterized by a body 24 that defines an externally threaded shaft 26,a bevel gear 30 and an end or seating shaft 28. The body 24 ispreferably, but not necessarily, unitary. The threaded shaft 26 extendsaxially from one side thereof in one direction from the center of thebevel gear 30 while the seating shaft 28 extends axially from anopposite side thereof in an opposite direction from the center of thebevel gear 30. The bevel gear 30 includes a plurality of teeth 32. Thenumber and spacing of the teeth 32 is matched to the number and spacingof teeth 52 of a bevel gear 50 of the adjustment assembly such that thebevel gears 30 and 50 mesh. As best seen in FIGS. 6 and 8, the body 24includes an axial bore 27 that extends through the threaded shaft 26,the bevel gear 30 and the seating shaft 28 thereby forming a cannulathat extends axially from on end of the body 24 to the other.

As best seen in FIGS. 6 and 8, the body 20 includes a threaded bore 57into which is received the threaded shaft 26 of the adjustment portion16. In order to prevent withdrawal of upper portion 14 from the lowerportion 12, the lower portion 12 includes the bore/stake 68 that extendsradially inward. The upper portion 14 includes a slot 70 terminating ina stop 71. The stake 68 extends into the slot 70 such that the upperportion 14 is confined in axial movement by the stake 68 within the slot70. When the upper portion 12 reaches its maximum upward height orposition, the stake 68 abuts the stop 71 thereby preventing furtherupward movement of the upper portion 12.

The adjustment assembly may include the adjustment portion 16 and theinput bevel assembly 49. The bevel assembly 49 is disposed in the lowerportion and particularly in and accessible by the bore 60. The bevelassembly 49 includes a D-shaped shaft 51 that is borne in bore 60 andalso retains a bevel gear 50. The input bevel assembly shaft 51 is fixedin rotational translation externally to the lower body 20 by aC-retaining ring 53 (see, e.g. FIG. 8). The bevel gear 50 meshes withthe bevel gear 30 of the adjustment portion 16. The bevel gear 50 isoffset 90° from the bevel gear 30. The shaft 51 further has a hex inputbore 65 that is configured to accept a hex driver. Other configurationsmay be used. Rotation of the shaft 51 via a hex driver rotates the bevelgear 50 which rotates the threaded shaft 26. Because the upper portion14 is fixed against rotation as described above, rotation of thethreaded shaft 26 causes the axial translation or movement of the upperportion 14 relative to the lower portion 12. Rotation of the bevelassembly 49 in one direction causes the rotation of the adjustmentportion 16 in one direction causing axial movement or translation of theupper portion 14 relative to the lower portion 12 in one direction whilerotation of the bevel assembly 49 in an opposite direction causes therotation of the adjustment portion 16 in an opposite direction causingaxial movement or translation of the upper portion 14 relative to thelower portion 12 in an opposite direction. Thus, the upper portion 14may be made to move up and down. Upward movement of the upper portion 14relative to the lower portion 12 increases the height of the spinalprosthesis 10. Because the adjustment is provided via a screw, there isinfinite height adjustment from a minimum to a maximum.

Referring to FIG. 11, there is depicted an exemplary embodiment of anendplate 76 for use with the spinal prosthesis 10. The endplate 76 isdefined by a circular body 77 and may come in various sizes. Theendplate 76 is configured to be received (press fit) onto the upper andlower ends 42 and 54 of the upper portion 14 and the lower portion 12respectively and to abut and/or be in contact with a vertebra. As such,the body 77 has a center bore 80 that is sized to be received on upperand lower ends 42 and 54 of the upper portion 14 and the lower portion12, respectively. The body 77 further has four generally oval cutouts81, 82, 83 and 84 that radially surround the center bore 80. The cutouts81, 82, 83 and 84 are spaced equidistant about the center bore 80, butnot necessarily so. The generally oval cutout 81 has a generally curvededge 85 proximate the periphery of the body 77 and a generally straightedge 86 proximate the center bore 80. This is shown in greater detail inFIG. 13 with respect to the endplate 94 of FIG. 12. Likewise, thegenerally oval cutout 82 has a generally curved edge 87 proximate theperiphery of the body 77 and a generally straight edge 88 proximate thecenter bore 80. Likewise, the generally oval cutout 83 has a generallycurved edge 89 proximate the periphery of the body 77 and a generallystraight edge 90 proximate the center bore 80. Likewise the generallyoval cutout 84 has a generally curved edge 91 proximate the periphery ofthe body 77 and a generally straight edge 92 proximate the center bore80. Moreover, the upper surface 78 of the body 77 includes a pluralityof spikes 79 that aid in seating the endplate 76 on the vertebra.

Referring to FIGS. 12 and 13, there is depicted another exemplaryembodiment of an endplate 94 for use with the spinal prosthesis 10. Theendplate 94 is defined by a generally kidney-shaped body 95 and may comein various sizes. and may come in various sizes. The endplate 94 isconfigured to be received (press fit) onto the upper and lower ends 42and 54 of the upper portion 14 and the lower portion 12 respectively andto abut and/or be in contact with a vertebra. As such, the body 94 has acenter bore 98 that is sized to be received on upper and lower ends 42and 54 of the upper portion 14 and the lower portion 12, respectively.The body 95 further has four generally oval cutouts 99, 100, 101 and 102that radially surround the center bore 98. The cutouts 99, 100, 101 and102 are spaced equidistant about the center bore 98, but not necessarilyso. As best seen in FIG. 13, the generally oval cutout 99 has agenerally curved edge 103 proximate the periphery of the body 95 and agenerally straight edge 104 proximate the center bore 98. This is shownin greater detail in FIG. 13. Likewise, the generally oval cutout 100has a generally curved edge 105 proximate the periphery of the body 95and a generally straight edge 106 proximate the center bore 98.Likewise, the generally oval cutout 101 has a generally curved edge 107proximate the periphery of the body 95 and a generally straight edge 108proximate the center bore 98. Likewise the generally oval cutout 102 hasa generally curved edge 109 proximate the periphery of the body 95 and agenerally straight edge 110 proximate the center bore 98. Moreover, theupper surface 96 of the body 95 includes a plurality of spikes 97 thataid in seating the endplate 94 on the vertebra.

Referring to FIG. 14 there is depicted a side view of an endplate 111having a body 112 that is representative of endplates 76 and 94. As suchthe body 112 has an upper surface 120 and a lower surface 122. The uppersurface 120 includes a plurality of spikes 120. FIG. 14 particularlyshows the angularity from one side 114 to another side 116 of the body112. The endplate 111 may be made having one of various angles. It iscontemplated that an endplate may come in five (5) different angles:−3.5°, 0°, 3.5°, 7° and 10.5°. Other angles may be used.

FIG. 10 depicts a modular height adjustable spinal prosthesis generallydesignated 10′. The spinal prosthesis 10′ is characterized by the heightadjustable spinal prosthesis 10 and endplates—here being round endplates76. As it can be seen, one endplate 76 is disposed on the hub 42 of theupper portion 14 while another endplate 76 is disposed on the hub 54 ofthe lower portion 12. The center bores of the endplates are sized toaccordingly fit onto the hubs. While a flat or 0° angle endplate isshown for the spinal prosthesis 10′, it should be understood that angledendplates may be used. The endplates 76 are also situated on therespective collars so as to be flat.

Referring to FIG. 15 there is depicted another exemplary embodiment of aheight adjustable, adjustable height and/or dynamic spinal prosthesisgenerally designated 160 fashioned in accordance with the principles ofthe present invention. The spinal prosthesis 160 may be considered arack and pinion style or type of height adjustable spinal prosthesis.The height adjustable spinal prosthesis 160 is characterized bycomponents fabricated from a biocompatible material such as stainlesssteel, titanium, a titanium alloy, composite, polymer or the like. Itshould be appreciated that the height adjustable spinal prosthesis 160is for use as a vertebral prosthesis, a vertebral body replacement(VBR), a spinal distraction device and/or a fusion device asappropriate. It should be further appreciated that the height adjustablespinal prosthesis 160 may be fabricated in various sizes as appropriateto accommodate different anatomy sizes.

The spinal prosthesis 160 is characterized by a lower body or portion162 and an upper body or portion 164. The lower and upper bodies 162,164 are generally cylindrical. The upper body 164 is axially adjustablerelative to the lower body 162. In this manner the spinal prosthesis 160is height adjustable. The lower body 162 has an internal bore 166 inwhich the upper body 164 is disposed. The lower body 162 has two pinions168, 170 that are constrained in translation such that they only rotate.The upper body 164 has twin racks 172, 174 on sidewalls thereof thatmesh respectively with the pinions 168, 170. Rotation of the pinions168, 170 in one direction causes the upper body 164 to axially move ortranslate in one direction relative to the lower body 162 while rotationof the pinions 168, 170 in an opposite direction causes the upper body164 to axially move or translate in an opposite direction relative tothe lower body 162. Upward translation of the upper body 164 relative tothe lower body 162 increases the height of the spinal prosthesis 160.The rack and pinion adjustment provides infinite height adjustment froma minimum height to a maximum height.

Referring to FIG. 16 there is depicted another exemplary embodiment of aheight adjustable, adjustable height and/or dynamic spinal prosthesisgenerally designated 180 fashioned in accordance with the principles ofthe present invention. The spinal prosthesis 180 may be considered arack and pinion style or type of height adjustable spinal prosthesis.The height adjustable spinal prosthesis 180 is characterized bycomponents fabricated from a biocompatible material such as stainlesssteel, titanium, a titanium alloy, composite, polymer or the like. Itshould be appreciated that the height adjustable spinal prosthesis 180is for use as a vertebral prosthesis, a vertebral body replacement(VBR), a spinal distraction device and/or a fusion device asappropriate. It should be further appreciated that the height adjustablespinal prosthesis 180 may be fabricated in various sizes as appropriateto accommodate different anatomy sizes.

The spinal prosthesis 180 is characterized by a lower body or portion182 and an upper body or portion 184. The lower and upper bodies 182,184 are generally cylindrical. The upper body 184 is axially adjustablerelative to the lower body 182. In this manner the spinal prosthesis 180is height adjustable. The lower body 182 has an internal bore 186 inwhich the upper body 184 is disposed. The lower body 182 has a pinion188 that is constrained in translation such that it only rotates. Theupper body 184 has a rack 190 on one sidewall thereof that meshesrespectively with the pinion 188. Rotation of the pinion 188 in onedirection causes the upper body 184 to axially move or translate in onedirection relative to the lower body 182 while rotation of the pinion188 in an opposite direction causes the upper body 184 to axially moveor translate in an opposite direction relative to the lower body 182.Upward translation of the upper body 184 relative to the lower body 182increases the height of the spinal prosthesis 180. The rack and pinionadjustment provides infinite height adjustment from a minimum height toa maximum height.

Referring to FIG. 17 there is depicted another exemplary embodiment of aheight adjustable, adjustable height and/or dynamic spinal prosthesisgenerally designated 200 fashioned in accordance with the principles ofthe present invention. The spinal prosthesis 200 may be considered arack and pinion style or type of height adjustable spinal prosthesis.The height adjustable spinal prosthesis 200 is characterized bycomponents fabricated from a biocompatible material such as stainlesssteel, titanium, a titanium alloy, composite, polymer or the like. Itshould be appreciated that the height adjustable spinal prosthesis 200is for use as a vertebral prosthesis, a vertebral body replacement(VBR), a spinal distraction device and/or a fusion device asappropriate. It should be further appreciated that the height adjustablespinal prosthesis 200 may be fabricated in various sizes as appropriateto accommodate different anatomy sizes.

The spinal prosthesis 200 is characterized by a lower body or portion202 and an upper body or portion 204. The lower and upper bodies 202,204 are generally cylindrical. The upper body 204 is axially adjustablerelative to the lower body 202. In this manner the spinal prosthesis 200is height adjustable. The lower body 202 has an internal bore 206 inwhich the upper body 204 is disposed. The upper body 202 has two pinions208, 210 that are constrained in translation such that they only rotate.The lower body 204 has twin racks 212, 214 on sidewalls thereof thatmesh respectively with the pinions 208, 210. Rotation of the pinions208, 210 in one direction causes the upper body 204 to axially move ortranslate in one direction relative to the lower body 202 while rotationof the pinions 208, 210 in an opposite direction causes the upper body204 to axially move or translate in an opposite direction relative tothe lower body 202. Upward translation of the upper body 204 relative tothe lower body 202 increases the height of the spinal prosthesis 200.The rack and pinion adjustment provides infinite height adjustment froma minimum height to a maximum height.

Referring to FIG. 18 there is depicted another exemplary embodiment of aheight adjustable, adjustable height and/or dynamic spinal prosthesisgenerally designated 220 fashioned in accordance with the principles ofthe present invention. The spinal prosthesis 220 may be considered aclamp style or type of height adjustable spinal prosthesis. The heightadjustable spinal prosthesis 220 is characterized by componentsfabricated from a bio-compatible material such as stainless steel,titanium, a titanium alloy, composite, polymer or the like. It should beappreciated that the height adjustable spinal prosthesis 220 is for useas a vertebral prosthesis, a vertebral body replacement (VBR), a spinaldistraction device and/or a fusion device as appropriate. It should befurther appreciated that the height adjustable spinal prosthesis 220 maybe fabricated in various sizes as appropriate to accommodate differentanatomy sizes.

The spinal prosthesis 220 is characterized by a lower body or portion222 and an upper body or portion 224. The lower and upper bodies 222,224 are generally cylindrical. The upper body 224 is axially adjustablerelative to the lower body 222. In this manner the spinal prosthesis 220is height adjustable. The lower body 222 has a collet 226 defining abore 227 surrounded by four (4) flanges 228, 229, 230 and 231. The upperbody 224 has an axial bore 225 and is situated in the bore 227 of thelower body 222. A clamp or band 234 surrounds the flanges 228, 229, 230and 231 and is tightened by a screw 236 extending through threadedflanges 240 and 242 thereof. Axial fixation of the upper body 224 in andrelative to the lower body 222 is achieved by tightening the clamp 234about the flanges 228, 229, 230 and 231 such that the flanges 228, 229,230 and 231 move radially inward. Height adjustment is thus accomplishedby positioning the upper body 224 within and relative to the collet 226and tightening the clamp 234.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly preferred embodiments have been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

What is claimed is:
 1. A spinal prosthesis comprising: a firstprosthetic portion having a body defining an interior chamber, whereinthe body includes a first hub extending from the body and a first collarextending axially between the body and the first hub, the first collaronly partially surrounding the first hub; a second prosthetic portion atleast partially received in the interior chamber of the first prostheticportion, the second prosthetic portion axially displaceable relative tothe first prosthetic portion, wherein the second prosthetic portionincludes a body, wherein the body of the second prosthetic portionincludes a second hub extending from the body and a second collarextending axially between the body and the second hub, the second collaronly partially surrounding the second hub; an adjustment mechanismcoupled to the first and second prosthetic portions within the bodies ofthe first and second prosthetic portions and operable to effect axialdisplacement of the second prosthetic portion relative to the firstprosthetic portion; a first end plate received on the first hub andsituated on the first collar of the first prosthetic portion; and asecond end plate received on the second hub and situated on the secondcollar of the second prosthetic portion; wherein the first collar isstructured to control an angular freedom of the first end plate; andwherein the second collar is structured to control an angular freedom ofthe second end plate.
 2. The spinal prosthesis of claim 1, wherein thesecond prosthetic portion includes a projection extending from the bodythat defines a cutout.
 3. The spinal prosthesis of claim 2, wherein thecutout at least partially receives at least a portion of the adjustmentmechanism when the second prosthetic portion is at a minimum axialdisplacement distance relative to the first prosthetic portion, andwherein the cutout provides a relatively larger gap between the firstprosthetic portion and the second prosthetic portion than in asurrounding region between the second prosthetic portion and the firstprosthetic portion in the interior chamber when the first and secondprosthetic portions are coupled together.
 4. The spinal prosthesis ofclaim 1, wherein the adjustment mechanism utilizes rotational motion toeffect axial displacement of the second prosthetic portion relative tothe first prosthetic portion.
 5. The spinal prosthesis of claim 4,wherein the adjustment mechanism includes a screw shaft and an inputbevel gear operable to rotate perpendicular to and in a meshingrelationship with the screw shaft for effecting the rotational motion.6. An implantable spinal prosthesis comprising: a first prostheticportion having a body defining an interior chamber; a second prostheticportion adapted for reception in the interior chamber of the firstprosthetic portion, the second prosthetic portion axially displaceablerelative to the first prosthetic portion, wherein engagement of thefirst prosthetic portion and the second prosthetic portion permit arelative longitudinal sliding movement; and an adjustment mechanismcoupled to the first and second prosthetic portions and operable toeffect axial displacement of the second prosthetic portion relative tothe first prosthetic portion, wherein the adjustment mechanism utilizesrotational motion for effecting axial displacement of the secondprosthetic portion relative to the first prosthetic portion, and whereinthe adjustment mechanism comprises: a screw shaft disposed in theinterior chamber and rotatably coupled to the second prosthetic portion,an input bevel gear disposed in the interior chamber, rotatably coupledto the first prosthetic portion, and adapted to rotate perpendicular toand in a meshing relationship with the screw shaft, and a threaded setpin extending through a port in the body of the first prosthetic portionand adjacent to the first bore, the threaded set pin structured toselectively engage and prevent rotation of the input bevel gear toprevent further axial displacement of the second prosthetic portionrelative to the first prosthetic portion.
 7. The implantable spinalprosthesis of claim 6, wherein the first prosthetic portion furtherincludes a first hub and a first collar that only partially surroundsthe first hub, the first collar extending axially between the body ofthe first prosthetic portion and the first hub; and wherein the secondprosthetic portion further includes a second hub and a second collarthat only partially surrounds the second hub, the second collarextending axially between the body of the second prosthetic portion andthe second hub.
 8. The implantable spinal prosthesis of claim 7, furthercomprising: a first end plate received on the first hub and situated onthe first collar of the first prosthetic portion; and a second end platereceived on the second hub and situated on the second collar of thesecond prosthetic portion; wherein the first collar is structured tocontrol an angular freedom of the first end plate, and wherein thesecond collar is structured to control an angular freedom of the secondend plate.
 9. The implantable spinal prosthesis of claim 8, wherein thefirst hub is cylindrical in shape; wherein the second hub is cylindricalin shape; wherein the first end plate has a central bore that is pressfit with the cylindrical first hub; and wherein the second end plate hasa central bore that is press fit with the cylindrical second hub. 10.The implantable spinal prosthesis of claim 6, wherein the secondprosthetic portion further includes a projection extending from the bodyand defining a cutout, wherein the cutout at least partially receivesthe input bevel gear when the second prosthetic portion is at a minimumaxial displacement distance relative to the first prosthetic portion;and wherein the cutout defines a relatively larger gap between the firstprosthetic portion and the second prosthetic portion than in asurrounding region between the first prosthetic portion and the secondprosthetic portion in the interior chamber when the first and secondprosthetic portions are coupled together.
 11. A spinal prosthesiscomprising: a first prosthetic portion having a body, the body definingan interior chamber; a second prosthetic portion adapted for axialdisplacement within the interior chamber of the first prosthetic portionrelative to the first prosthetic portion whereby height of the spinalprosthesis is varied, the second prosthetic portion having a body and aprojection extending from the body that defines a cutout; an adjustmentmechanism coupled to the first and second prosthetic portions andoperable to effect axial displacement thereof; wherein the cutout atleast partially receives at least a portion of the adjustment mechanismwhen the second prosthetic portion is at a minimum axial displacementdistance relative to the first prosthetic portion, and wherein thecutout defines a relatively larger gap between the first prostheticportion and the second prosthetic portion than in a surrounding regionbetween the second prosthetic portion and the first prosthetic portionin the interior chamber when the first and second prosthetic portionsare coupled together.
 12. The spinal prosthesis of claim 11, wherein thebody of the second prosthetic portion defines an opening to provideaccess to the interior chamber, wherein the interior chamber and theopening are configured to receive bone growth material.
 13. The spinalprosthesis of claim 11, wherein the first prosthetic portion furtherincludes a first hub and a first collar that only partially surroundsthe first hub, the first collar extending axially between the body ofthe first prosthetic portion and the first hub; and wherein the secondprosthetic portion further includes a second hub and a second collarthat only partially surrounds the second hub, the second collarextending axially between the body of the second prosthetic portion andthe second hub.
 14. The spinal prosthesis of claim 13, wherein the firsthub is cylindrical in shape; wherein the second hub is cylindrical inshape; wherein the first end plate has a central bore that is press fitwith the cylindrical first hub; and wherein the second end plate has acentral bore that is press fit with the cylindrical second hub.
 15. Thespinal prosthesis of claim 14, wherein the cutout at least partiallyreceives the input bevel gear when the second prosthetic portion is at aminimum axial displacement distance relative to the first prostheticportion.
 16. The spinal prosthesis of claim 11, wherein the adjustmentmechanism includes: a bevel assembly having a configured input socketextending at least partially through the first bore in the firstprosthetic portion, and an input bevel gear coupled to the input socketand disposed in the interior chamber, the input socket and input bevelgear having a first rotational axis perpendicular to a longitudinal axisof the interior chamber; a bevel gear ninety degrees offset from theinput bevel gear and disposed in the interior chamber, the bevel gearhaving a second rotational axis perpendicular to the first rotationalaxis; a threaded shaft extending from the bevel gear and coupled to thethreaded bore of the second prosthetic portion; and a threaded set pinconfigured to engage the input bevel gear and prevent further axialdisplacement of the second prosthetic portion relative to the firstprosthetic portion; wherein rotation of the input socket rotates theinput bevel gear about the first rotational axis, which rotates thebevel gear about the second rotational axis, which rotates the threadedshaft, which effects axial displacement of the second prosthetic portionrelative to the first prosthetic portion.
 17. The spinal prosthesis ofclaim 11, wherein the body of the first prosthetic portion includes awall contour defining a first axial guide; wherein the body of thesecond prosthetic portion includes a wall contour defining a secondaxial guide; where the first axial guide is structured to receive thesecond axial guide to permit relative longitudinal sliding movement andinhibit relative rotational movement between the second prostheticportion and the first prosthetic portion.
 18. The spinal prosthesis ofclaim 11, wherein the adjustment mechanism utilizes rotational motion toeffect axial displacement of the second prosthetic portion relative tothe first prosthetic portion.